1. Field of the Invention
The present invention relates to a copper alloy wire suitable for a conductor for use in wirings for magnetic heads, and insulated electric wires and multiple core parallel bonded wires including the copper alloy wire as a conductor. More particularly, the present invention relates to those which are suitable for use as fine wires having excellent electroconductivity, tensile strength and elongation and having a wire diameter of no larger than 90 .mu.m.
2. Prior Art
Recently, there has been rapidly increased a demand for fine copper wires having a wire diameter of no larger than 0.1 mm, particularly those having a wire diameter of no larger than 50 .mu.m in the field of copper wires and core wires for magnetic head windings along with the development of electronic devices.
Along with the fining of copper wires, however, there have arisen some problems that upon winding of wires breakage of the wires tends to occur and the terminals of the wires tend to be bent. For example, when a copper fine wire is wound around the ferrite core portion of a magnetic head through its window portion, it will be difficult to pass the wire through the window portion if the terminals of the wire are bent. If this did actually occur, emergency measures could be taken in the case where winding was carried out by manual operation. However, in automatic winding steps using robots whose introduction has recently been accelerated for labor-saving, the occurrence of such breakage or bending of wires unavoidably leads to reduction in productivity. Therefore, copper fine wires used as a core wire of a magnetic head winding are required to have increased tensile strength, elongation, as well as improved bending resistance without decreasing in electroconductivity.
However, when copper fine wires are formed by a drawing method comprising drawing a copper wire stock to a high reduction ratio which is a method generally used for increasing the tensile strength of copper wires, the elongation of wire decreases so that desired elongation cannot be obtained and electroconductivity of the resulting fine wire is deteriorated. On the other hand, when the copper fine wire obtained by reduction is annealed to fully soften in order to increase elongation, there arises a problem that no desired tensile strength and bending resistance can be obtained.